1. Field of the Invention
The present invention relates generally to the field of shaft encoders and more specifically to an improved shaft encoder which provides a pulsed output signal upon rotation of a shaft, the improvement relating to the low cost, reliability and simplicity of the encoder of the invention.
2. Prior Art
Shaft encoders provide electrical signals indicative of a shaft's angular position, speed of rotation and direction. Modern shaft encoders typically provide an output in the form of a series of electrical pulses the rate of which is proportional to the rotational rate of the shaft. The angular resolution of the shaft encoder is dependent upon the number of pulses generated per revolution of the shaft. The larger the number of pulses per revolution, the more complex and sophisticated is the encoder and therefore the more costly. Moreover, the complexity of the encoder leads to a reduction in reliability because there are more components that could become faulty or inoperative. However, there are applications for shaft encoders where less precise resolution is needed such as within 5 or 10 degrees as opposed to tenths of a degree. Unfortunately there are no prior art shaft encoders which fully exploit a reduction in resolution requirements. As a result, even low resolution shaft encoders are relatively expensive and unreliable and are still sufficiently complex to make size reduction a still formidable challenge.
There is therefore an ongoing need for a low cost, highly reliable shaft encoder capable of modest angular resolution and which can be made in relatively small package sizes.